A brayton cycle generally refers to a type of engine model in which a compressor works in conjunction with an expander to generate mechanical energy from a heat source that heats a fluid flow between the compressor and expander. A gas-turbine engine or jet engine are examples of engines that function according to the brayton cycle. An open brayton cycle is a particular type of brayton cycle in which the working fluid is open to the atmosphere; that is, the working fluid is air.